As the lifestyle of the Japanese people becomes more westernized and the aging of the population continues to progress rapidly, the number of patients with lifestyle-related diseases such as ischemic heart disease, cerebrovascular disease and diabetes continues to increase. One of the major causes of these types of lifestyle-related diseases is obesity, and the importance of preventing and remedying obesity is widely stressed. Further, obesity is also seen as undesirable from the viewpoints of appearance and beauty, and there is much interest in dieting for the purpose of preventing or remedying obesity.
Against this type of background of heightened awareness of obesity, a diagnostic criterion known as “metabolic syndrome” has been identified as increasing the probability of the future onset of lifestyle-related disease, and measurement of the waist circumference is used in medical checkups with the purpose of preventing and/or remedying metabolic syndrome.
Examples of methods that are conventionally used for addressing obesity include dietary treatments (dietary restriction and fasting), exercise-based treatments (promoting energy consumption through exercise), and drug-based treatments. Examples of the drugs currently used in drug-based treatments include Orlistat, which inhibits the absorption of fat in the intestinal tract (such as the drugs “Xenical” (a registered trademark) manufactured by Roche Ltd., and “Alli” (a registered trademark) manufactured by GlaxoSmithKline plc.), and Acarbose, which is an inhibitor of the glycolytic enzyme (α-glucosidase) (such as the drug “Glucobay” (a registered trademark) manufactured by Bayer AG).
However, excessive use of these treatments can cause a number of problems, including impairment of the health of the patient, weight increase due to rebound, and difficulty in achieving continuous or long-term treatment. Particularly in the case of the drug-based methods, side effects tend to also be a problem. Further, the drugs used in the drug-based treatments are pharmaceutical drugs, and are not particularly easy to use.
Tests on inhibiting obesity using microbes such as lactic acid bacteria have been previously reported. For example, Non-Patent Document 1 reports that when a feed containing 10% of live dried Bifidobacterium bifidum G9-1 was fed to exogenously hypercholesterolemic (ExHC) rats, obese (Wistar fatty) rats, and obese and diabetic (KK-Ay) mice, the levels of triacylglycerol and cholesterol in the blood and liver decreased. However, when the above bacterial strain is used, a large amount of the bacteria must be mixed into the feed to obtain the above effects, and ensuring routine and continuous ingestion of the effective amount is difficult.
Furthermore, conjugated linoleic acid (CLA) is known to exhibit physiological activity including an anti-obesity action. For example, Non-Patent Document 2 reports an animal study in which mixing CLA into feed in amounts of 0, 0.25, 0.5 and 1% revealed that, at amounts of 0.5% or higher, body weight and body fat were reduced in a concentration-dependent manner.
In relation to CLA, it is known that bacteria such as those of the genus Bifidobacterium have the ability to convert linoleic acid (LA) into CLA (CLA conversion function), and various techniques have been proposed that utilize these bacteria. For example, Patent Document 1 discloses that the Bifidobacterium breve CBG-C2, Bifidobacterium pseudocatenulatum CBG-C4 and Enterococcus faecium CBG-05 all exhibit superior CLA conversion functonality, and Table 1 discloses that the Bifidobacterium breve CBG-C2 converted LA to CLA with a high CLA conversion rate of 54.7%. Further, Patent Document 1 also discloses the use of CLA-generating compositions comprising these bacterial strains as active ingredients in the prevention or treatment of diseases that are inhibited by CLA (such as cancer, arterial sclerosis, diabetes and obesity).
However, when CLA or bacteria having a superior CLA conversion function are administered as part of a diet aimed at either treating obesity or preventing obesity, there is a danger that side effects may occur.
As an example of these CLA side effects, Non-Patent Document 3 reports that when 1% of CLA was mixed with mice feed and administered over an 8-month period, atrophy of the adipose tissue, an increase in the insulin level, and a reduction in glucose tolerance were all observed. Further, Non-Patent Document 4 reports that when humans ingested approximately 3 g of CLA daily over a continuous period, glucose tolerance tended to worsen, as evidenced by a decrease in insulin sensitivity and an increase in oxidation markers in the urine.
Furthermore, the average LA ingestion amount by Japanese people is approximately 11 g (see Non-Patent Document 5), and therefore if bacteria having a high CLA conversion function is administered, CLA will be produced in large amounts. For example, if 11 g of LA is converted to CLA with the above-mentioned conversion rate of 54.7%, then 6.02 g of CLA will be produced. If a large amount of CLA is produced in this manner, then the above-mentioned side effects become a concern.